l. Field of the Invention
This invention relates to a method of manufacturing a hardwearing aluminum alloy part from quench-solidified Al-Si alloy powder.
2. Description of the Prior Art
Recently there has been put into practice a technique where a hardwearing aluminum alloy part is manufactured by hot-forging an extruded form which has been formed by extruding quench-solidified Al-Si alloy powder. Conventionally, when the hot forging is effected, the extruded form is heated to a temperature (400.degree. to 500.degree. C.) at which the extruded form can have adequate ductility and which is lower than the temperature at which Si particles remarkably coarsen (about 550.degree. C.).
Since in the hardwearing aluminum alloy part formed of the quench-solidified Al-Si alloy powder, a higher a proportion of Si (20 to 30 wt %) alloys than in a cast aluminum alloy part (not higher than 18 wt %), the hardwearing aluminum alloy part is excellent in resistance to wear, and since the Si particles in the primary phase are very fine (not larger than 10 .mu.m) in the hardwearing aluminum alloy part formed of the quench-solidified Al-Si alloy powder, the hardwearing aluminum alloy part formed of the quench-solidified Al-Si alloy powder is easy to plastically process and is excellent in strength.
However, the hardwearing aluminum alloy part formed of the quench-solidified Al-Si alloy powder is disadvantageous in that it is not so excellent in resistance to wear for its large Si content due to excessively fine Si particles in the primary phase.
In order to overcome such a disadvantage and to coarsen the Si particles, thereby improving the resistance to wear of the hardwearing aluminum alloy part formed of the quench-solidified Al-Si alloy powder, it has been proposed, as disclosed for instance in Japanese Unexamined Patent Publication No. 61(1986)-166931, to heat the extruded form of quench-solidified Al-Si alloy powder under conditions which satisfies the following formula. EQU T+40 .sub.log t.gtoreq.520
wherein T represents the heating temperature (.degree.C.) and t represents the heating time (hour).
However, this approach gives rise to another problem that numbers of blisters are formed in the surface or near the surface of the aluminum alloy part due to residual gas in the powder which quickly expands since the powder is heated for a long time (e.g., 5 hours) at a high temperature (e.g., about 520.degree. C.), and accordingly it is difficult to manufacture an aluminum alloy part for practical use. Further, since the approach requires a long heat treatment, too much heat energy is consumed.